THROMBIN AND ALBUMIN ADSORPTION TO PVA AND HEPARIN PVA HYDROGELS .2. COMPETITION AND DISPLACEMENT

Thrombin adsorption to polyvinyl alcohol (PVA) was different from its adsorption to polyethylene (PE)-not so much in amount, but in its affinity. Thrombin was more easily displaced from polyethylene and its adsorption was more readily prevented by prior or simultaneous exposure to albumin. From PVA (or heparin-PVA), only approximately 30% of the adsorbed protein could be removed by a series of eluents, including even harsh ones such as 2.5M NaOH and 6M guanidine; >85% could be removed from PE. Thrombin adsorption to PVA was not affected by the presence of BSA in solution or at the surface, but was virtually prevented on PE by preexposure to or adsorption with BSA. Heparin-PVA was not much different than PVA in most of these experiments, but did exhibit a ''Vroman effect''. In the absence of fibrinogen or antithrombin III, there was a maximum in thrombin adsorption from plasma at a plasma concentration of 1%. The behavior on this surface was dependent on both exposure time and protein concentration. These studies highlight the complexity of the interaction between plasma proteins and polymer surfaces (particularly hydrogel surfaces) and the difficulty of obtaining a clear picture of what happens when a single protein interacts with a polymer in the presence of other proteins.